Implantable medical devices such as pacemakers and cardioverter defibrillators are configured to monitor the electrical activity in various chambers of a patient's heart. In doing so, the devices can assess whether cardiac activity is consistent with desired cardiac function or whether abnormalities, such as arrhythmias, are present. The devices are usually programmed to deliver remedial therapy, typically in the form of the selective delivery of cardiac stimulation pulses, for bradycardia pacing, antitachycardia pacing, cardioversion and defibrillation therapy.
As is recognized in the field, the initiation of remedial treatment solely based upon the detection of arrhythmias, such as tachycardia and fibrillation, requires considerable preparation time and sometimes places the patient at risk due to the severity of the cardiac condition just prior to the initiation of therapy. This is particularly true for conditions involving ventricular tachyarrhythmias and fibrillation. Without rapid remedial response to ventricular tachyarrhythmias and fibrillation, the likelihood of patient death is relatively high. The mechanisms for developing appropriate remedial cardiac stimulation pulses require finite and often lengthy time periods. Obviously, the greater the time required to monitor cardiac activity and deliver therapy, the greater the potential for patient injury and death.
Implantable cardiac stimulation devices that maintain a constant monitor of cardiac activity for the purposes of predicting the onset of a cardiac arrhythmia provides a “first alert” so as to place the stimulation device at the “ready” to deliver therapy. Preferably and advantageously, providing therapy prior to the onset of an arrhythmia would not only put less strain and demand on the stimulation device but would also maintain the patient in the least traumatized state. As a further consideration, it would be advantageous to provide a second test to confirm the necessity of delivering therapy once a prediction of arrhythmia has been made so as to avoid response to “false positives”.
Accordingly, an implantable medical device configured to predict the onset of cardiac arrhythmia, while utilizing a confirmatory test to trigger delivery of therapy would be most preferable. In such case, therapy would then be provided with the highest confidence of necessity.